It is known that the operating sequences in a longwall working, such as in particular the operating movement of the plough, the shifting of a scraper-chain conveyor carrying the plough guide and the displacement of the advancing supports, can all be controlled from a central control station. To achieve complete longwall control, which is a condition for automation of winning operations, the operating data which are relevant for this purpose, such as in particular the respective operating position of the plough, its cutting depth, the state of the face conveyor and of the plough guide in the longwall as well as the location of the advancing support units with respect to the working face and the face conveyor are determined and are fed to the control station. The control station can be equipped with a computer and with an operator's control terminal having a keypad for keying in a control program and with a screen for visual display of the respective face conditions. With electro-hydraulic support control means, there are allocated to the individual support units of the face, individual control devices which are connected to the central control station via data and command lines.
During the mechanical winning of the longwall, the support units which are arranged next to one another in a row behind the face conveyor are re-located individually in sequence after passage of the plough once the face conveyor has been moved forward. The known support control means selectively operate with individual control, sequence control and group order control. With automated winning the central control station carries out the staged shifting of the face conveyor and the shifting up of the advancing supports as a function of the operating movements of the plough.
During the ploughing of coal, ploughing in long strokes is aimed for to attain high outputs. Furthermore, it is generally desirable to keep the working face and therefore the longwall in a rectilinear course as far as possible. To enable the course of the working head in a winning longwall to be influenced with conveyor-bound supports controlled by a central station, it is known, for example, to detect the support and conveyor movements with sensors which are connected to the central station computer so that the respective actual conveyor line and the respective actual support line can be detected by means of the computer. The conveyor line and the support line thus form computer reference data lines during the shifting of the conveyor and during the following up of the supports. As the individual shifting rams are equipped with sensors for detecting the relative movement between the conveyor and the associated support units, deviations from a defined support line can be established and compensated by means of the computer via the determined actual reference lines (see U.S. Pat. No. 4887935).
A process for the electro-hydraulic control of plough and advancing support units in an automated longwall is also known in which the plough guided on the face conveyor operates with winning cuts extending substantially over the entire length of the longwall and in which, moreover, the support units linked to the conveyor with their rams can be moved forward in groups as a function of the measured extension lengths of the rams. The electro-hydraulic control means again comprises a central control station with a plough position display. The individual working steps in the longwall are controlled from the control station, to which all significant measured values from the longwall are transmitted. During each ploughing run, only one support group comprising several mutually adjacent support units of the entire support row along the longwall is shifted by the cutting depth of the plough or a multiple thereof (see U.S. Pat. No. 4964675).
Finally, for avoiding a machine stable which is to be excavated at the longwall ends, it is known to move the plough to and fro several times in the end region of the longwall in order to produce a "break-in" of the face, from which the plough can begin its winning operation (See DE-PS 18 09 713).